Oral tradition in Commentary

We have Nikaya-Memorizers from 0 BE till now. Monks have the rules to memorize Sutta when growing up.
DN Commentary:

etenevupāyena asītibhāṇavāraparimāṇaṃ khandhakaṃ, pañcavīsatibhāṇavāraparimāṇaṃ parivārañca saṅgahaṃ āropetvā ‘‘idaṃ vinayapiṭakaṃ nāmā’’ti ṭhapesuṃ . vinayapiṭakāvasānepi vuttanayeneva mahāpathavikampo ahosi. taṃ āyasmantaṃ upāliṃ paṭicchāpesuṃ – ‘‘āvuso, imaṃ tuyhaṃ nissitake vācehī’’ti.
...
tadanantaraṃ mahāvaggaṃ, tadanantaraṃ pāthikavagganti, evaṃ tivaggasaṅgahaṃ catutiṃsasuttapaṭimaṇḍitaṃ catusaṭṭhibhāṇavāraparimāṇaṃ tantiṃ saṅgāyitvā ‘‘ayaṃ dīghanikāyo nāmā’’ti vatvā āyasmantaṃ ānandaṃ paṭicchāpesuṃ – ‘‘āvuso, imaṃ tuyhaṃ nissitake vācehī’’ti.
tato anantaraṃ asītibhāṇavāraparimāṇaṃ majjhimanikāyaṃ saṅgāyitvā dhammasenāpatisāriputtattherassa nissitake paṭicchāpesuṃ – ‘‘imaṃ tumhe pariharathā’’ti.
tato anantaraṃ satabhāṇavāraparimāṇaṃ saṃyuttanikāyaṃ saṅgāyitvā mahākassapattheraṃ paṭicchāpesuṃ – ‘‘bhante, imaṃ tumhākaṃ nissitake vācethā’’ti.
tato anantaraṃ vīsatibhāṇavārasataparimāṇaṃ aṅguttaranikāyaṃ saṅgāyitvā anuruddhattheraṃ paṭicchāpesuṃ – ‘‘imaṃ tumhākaṃ nissitake vācethā’’ti.
tato anantaraṃ dhammasaṅgahavibhaṅgadhātukathāpuggalapaññattikathāvatthuyamakapaṭṭhānaṃ abhidhammoti vuccati. evaṃ saṃvaṇṇitaṃ sukhumañāṇagocaraṃ tantiṃ saṅgāyitvā – ‘‘idaṃ abhidhammapiṭakaṃ nāmā’’ti vatvā pañca arahantasatāni sajjhāyamakaṃsu. vuttanayeneva pathavikampo ahosīti. Translation:

As I've explained, 500 bhikkhus in first council recited 80 Bhanavara of Khandhaka (VN.Bhikkhu,Bhikkhuni,Maha,Cula) and 25 Bhanavara of Parivara together, then called it Vinaya-Pitaka. At the end of reciting, the land shook. 500 bhikkhus in first council ordered Upali "Teach VinayaPitaka to your students, Avuso".
...
500 bhikkhus in first council recited 64 Bhanavara in systematized language which included 34 Sutta 3 Vagga step by step (SilakkhandhaVagga, Mahavagga, Pathikavagga) together, then called it DigaNikaya and ordered Ananda "Teach DigaNikaya to your students, Avuso".
Then 500 bhikkhus in first council recited MajjhimaNikaya 80 Bhanavara together, and
they ordered Sariputta's students "Keep it, Avuso".
Then 500 bhikkhus in first council recited SamyuttaNikaya 100 Bhanavara together, and
they ordered Kassapa "Teach SamyuttaNikaya to your students, Bhante".
Then 500 bhikkhus in first council recited AnguttaraNikaya 120 Bhanavara together, and
they ordered Anuruddha "Teach AnguttaraNikaya to your students, Avuso".

The Rule

in commentary according to V.N. Mahākhandhaka:**

Qualities of nissayamuccaka-bhikkhu (teaching lay people)

1. Proficient to recite pāṭimokkha-pāli and to understand it's commentary.
2. Proficient to recite and to understand 4 bhāṇavāra (~1,000 syllable) of sutta and their commentary, to teach laymen on uposatha day.
3. Proficient to recite and to understand sutta for bhikkhu's life such as andhakavindasutta, mahālahulovādasutta, ambaṭṭhasutta, etc.
4. Proficient to recite and to understand sutta for teaching in 3 chances: banquet for saṅgha by layman (nidhikaṇdasutta), funeral ceremony (tirokuṭṭasutta), and auspicious ceremony (maṅgalasutta).
5. Enough understand to judge/to decide about saṇgha's ceremony such as uposatha, pavāraṇā, etc.
6. Proficient to recite and to understand his kammaṭṭhānā throughout the nibbāna-course.
7. 5 years experience in monk hood as a monk.

Qualities of bhikkuparisūpaṭṭhāpaka-bhikkhu (teaching bikkhus)
If above layman's teachers want to teach bhikkhus (ūpajjhā-ācāriya, nissaya-ācāriya), they must increase their skill level to all of the following qualities.
These are for abhivinaya teaching:

1. Proficient to recite mahāvibhagha and bhikkhunivibhaṅga (first 3 books of thai 45 books pali-tipitaka) of vinaya-pitaka-pali. At least, he can relay with the other 3 bhikkhu. Proficient to understand it's commentary, too.
2. Proficient to recite all saṇgha's ceremony in vinaya-pitaka mahāvagga and julavagga.
3. Proficient to recite 14 vatta in vattakhandhaka.

These are for abhidhamma (kammaṭṭhāna) teaching:

4. Proficient to recite one of this suttanta-pali: mūlapaṇṇassa (1st/3 parts of M.N.) for student in M.N. faculty, mahāvagga (2nd/3 parts of D.N.) for student in D.N. faculty, sagāthavagga+nidānavagga+khandhavāravagga of S.N. or mahāvagga of S.N. for student in S.N. faculty, before half of A.N. or after half of A.N. or ekakanipāta+dukanipāta of A.N. for student in A.N. faculty, jātaka+commentary (because kammaṭṭhāna was described in commentary) for student in jātaka faculty.

Qualities of bhikkunovdaka-bhikkhu (teaching bhikkunīs)
If above layman's teachers want to teach bhikkhunī, they must increase their skill level to all of these qualities:

1. Proficient to recite whole tipitaka-pali and commentary-pali. Or at least, he still must recite whole tipitaka, but he can recite just one commentary of suttanta, first 4 parts of commentary of 7 parts of abhidhamma. However, vinaya-commentary is what he must recite it all.

Reference: tipitaka and commentary of vinaya pācittiyakaṇḍa bhikkhunovādakasikkhāpada and vinaya mahāvagga mahākhandhaka.

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Related topic: https://buddhism.stackexchange.com/a/22917/10100 https://buddhism.stackexchange.com/a/23663/10100

How can SukkhaVipassaka enlighten Nibbana without Appanā Jhāna.

SukkhaVipassaka can enlighten Arahatraphala without order from 9 samapatti. This kind of people must has less 5 hindrances from his birth to enlighten in 7 years, or more than that for TanhaCarita MandaPuggala (too much hindrances who avoid to practice Jhana and no knowledge in Paticcasamuppada). However, most Arahanta attain 6 Abhiñña as well according to Theragatha, so I think Arahanta try to practice 9 Samapatti after enlightenment too. The same as Arahanta try to memorize Buddha's teaching which commentary commented BhandāgāikaPariyatti (Nikaya Memorizer) is duty of Arahanta directly